Addition Of Ammonia Research Articles

Phytoplankton transcriptomic and physiological responses to fixed nitrogen in the California current system.

Marine phytoplankton are responsible for approximately half of photosynthesis on Earth. However, their ability to drive ocean productivity depends on critical nutrients, especially bioavailable nitrogen (N) which is scarce over vast areas of the ocean. Phytoplankton differ in their preferences for N substrates as well as uptake efficiencies and minimal N requirements relative to other critical nutrients, including iron (Fe) and phosphorus. In this study, we used the MicroTOOLs high-resolution environmental microarray to examine transcriptomic responses of phytoplankton communities in the California Current System (CCS) transition zone to added urea, ammonium, nitrate, and also Fe in the late summer when N depletion is common. Transcript level changes of photosynthetic, carbon fixation, and nutrient stress genes indicated relief of N limitation in many strains of Prochlorococcus, Synechococcus, and eukaryotic phytoplankton. The transcriptomic responses helped explain shifts in physiological and growth responses observed later. All three phytoplankton groups had increased transcript levels of photosynthesis and/or carbon fixation genes in response to all N substrates. However, only Prochlorococcus had decreased transcript levels of N stress genes and grew substantially, specifically after urea and ammonium additions, suggesting that Prochlorococcus outcompeted other community members in these treatments. Diatom transcript levels of carbon fixation genes increased in response to Fe but not to Fe with N which might have favored phytoplankton that were co-limited by N and Fe. Moreover, transcription patterns of closely related strains indicated variability in N utilization, including nitrate utilization by some high-light adapted Prochlorococcus. Finally, up-regulation of urea transporter genes by both Prochlorococcus and Synechococcus in response to filtered deep water suggested a regulatory mechanism other than classic control via the global N regulator NtcA. This study indicated that co-existing phytoplankton strains experience distinct nutrient stresses in the transition zone of the CCS, an understudied region where oligotrophic and coastal communities naturally mix.

A novel phenylalanine ammonia-lyase from Pseudozyma antarctica for stereoselective biotransformations of unnatural amino acids

A novel phenylalanine ammonia-lyase of the psychrophilic yeast Pseudozyma antarctica (PzaPAL) was identified by screening microbial genomes against known PAL sequences. PzaPAL has a significantly different substrate binding pocket with an extended loop (26 aa long) connected to the aromatic ring binding region of the active site as compared to the known PALs from eukaryotes. The general properties of recombinant PzaPAL expressed in E. coli were characterized including kinetic features of this novel PAL with l-phenylalanine (S)-1a and further racemic substituted phenylalanines rac-1b-g,k. In most cases, PzaPAL revealed significantly higher turnover numbers than the PAL from Petroselinum crispum (PcPAL). Finally, the biocatalytic performance of PzaPAL and PcPAL was compared in the kinetic resolutions of racemic phenylalanine derivatives (rac-1a-s) by enzymatic ammonia elimination and also in the enantiotope selective ammonia addition reactions to cinnamic acid derivatives (2a-s). The enantiotope selectivity of PzaPAL with o-, m-, p-fluoro-, o-, p-chloro- and o-, m-bromo-substituted cinnamic acids proved to be higher than that of PcPAL.

Bulky Cations Improve Band Alignment and Efficiency in Sn-Based Perovskite Solar Cells

The commercial feasibility of perovskite solar cells (PSCs) is not guaranteed as long as lead (Pb) is present in the active material, halide perovskites. Mixed halide Tin (Sn)-based alloyed perovskites with optimal band gaps ranging from 1.15 to 3.55 eV are excellent alternatives to Pb-based perovskites. In this work, we find that the addition of bulky phenylethyl ammonium (PEA) cation in the precursor solution leads to improved solar cell performance and optoelectronic properties. A prolonged laser exposure is found to induce a redshift the sample absorption for the control and no shift for the PEA-added sample, as shown by transient absorption spectroscopy. Further, we show that the addition of PEA improves band alignment of the perovskite with phenyl-C61-butyric acid methyl ester (PCBM), which aids in electron injection and therefore increases photocurrents in solar cells. These results show that PEA addition suppresses halide segregation improving material stability, charge collection at perovskite/electron transport layer, and recombination dynamics in perovskite material. As a result, the PEA-containing Sn-rich PSCs exhibited a champion efficiency of 13% with a high open-circuit voltage of 0.77 V and improved current-voltage hysteretic behavior. These results shed light on the importance of halide segregation and band alignment when designing lead-free PSCs.

The effect of ammonia addition on the low-temperature autoignition of n-heptane: An experimental and modeling study

Ammonia (NH3) is receiving increasing attention as an alternative engine fuel due to its carbon-free nature. However, its fundamental combustion characteristics, such as higher autoignition temperature and lower burning velocity compared to conventional hydrocarbons, limit its direct use in traditional engines. To confront this dilemma, hydrocarbon/NH3 blending fuels are seen as one of the most appropriate ways to exploit its advantage and offset its weaknesses. Using n-heptane as a representative of hydrocarbons, this study investigated the effect of NH3 addition on the low-temperature autoignition of n-heptane. The ignition delay times of five n-heptane/NH3 mixtures with NH3 fractions of 0%, 20%, and 40% were measured in a rapid compression machine at temperatures of 635–945 K, pressures of 10 and 15 bar, and equivalence ratios of 1.0 and 2.0. Experimental results show that the n-heptane/NH3 blending fuels exhibit pronounced low-temperature reactivity, and both the total and the first-stage ignition delay times increase with the increase of NH3 fraction. A blending mechanism of n-heptane/NH3 was compiled based on the existing n-heptane mechanism and NH3 mechanism. It is found that the blending mechanism is capable to predict the inhibition effect of NH3 addition on n-heptane autoignition and qualitatively capture the dependence of ignition delay time on equivalence ratio and oxygen mole fraction. Nevertheless, there are significant discrepancies between the experiments and the simulation. Furthermore, kinetic analyses, including species evolution, rate of production and sensitivity of OH radical were conducted sequentially to reveal the autoignition kinetics of NH3/n-heptane blends and the interaction between n-heptane and NH3. Suggestions are provided for the further development of the blending mechanism.

Biosynthesis of hydrazine from ammonium and hydroxylamine using an anaerobic ammonium oxidizing bacterium.

To synthesize hydrazine (N2H4) from ammonium and hydroxylamine (NH2OH) using an anaerobic ammonium oxidation (anammox) bacterium, Candidatus Kuenenia stuttgartiensis. K. stuttgartiensis cells were anoxically cultivated with the addition of ammonium (2mM) and NH2OH (1-100mM) at pH 6-10.5, and 4-65°C to examine the favorable cultivation conditions for N2H4 production. The influence of NH2OH concentration was more prominent than that of pH and temperature, and NH2OH concentration higher than 1mM deteriorated N2H4 yields significantly. The following conditions were found to be favorable for N2H4 production using K. stuttgartiensis cells: pH 9, 38°C, and < 1mM NH2OH. In a continuous-feed system operated at these conditions, K. stuttgartiensis cells produced N2H4 with a maximum concentration of 0.65mM, which is the highest N2H4 concentration previously reported in biological processes. Optimal cultivation conditions for K. stuttgartiensis for N2H4 production were successfully determined, and the present study is the first to document potential biological N2H4 production using anammox bacteria.

Area-selective chemical vapor deposition of cobalt from dicobalt octacarbonyl: Enhancement of dielectric-dielectric selectivity by adding a coflow of NH3

The authors describe the enhancement of the area-selective chemical vapor deposition of cobalt films on one oxide surface over another from the precursor Co2(CO)8 by addition of the nucleation inhibitor ammonia (NH3). In the absence of an NH3 coflow, the Co2(CO)8 precursor exhibits a weak intrinsic selectivity: at 70 °C, Co nucleates quickly on Al2O3 but more slowly on SiO2. The addition of an NH3 coflow, however, greatly amplifies the selectivity between different oxide surfaces. Thus, NH3 significantly inhibits nucleation on acidic oxides such as SiO2 and WO3 but has little effect on more basic oxides such as Al2O3, HfO2, and MgO. Comparison of growth on fully hydroxylated and dehydroxylated SiO2 suggests that hydroxyl groups are the nucleation sites that are affected by the addition of NH3. The mechanism of nucleation appears to be disproportionation of Co2(CO)8 to Co2+ (the intermediate that leads to nucleation) and Co(CO)4−: this disproportionation occurs readily on basic oxides but not on acidic oxides. The addition of NH3 has little effect on Co nucleation on basic oxides, probably because ammonia binds poorly to such surfaces, but NH3 greatly retards nucleation on acidic oxides such as SiO2; the authors propose that the latter result is either a site blocking effect or the result of conversion of Co2+ to inactive Co(NH3)x2+ species. Nucleation of cobalt is facile on gold (a very unreactive metal) even in the presence of NH3. The authors have found, however, that the deposition of Co on tungsten can be inhibited by exposing the surface briefly to ozone; no deposition occurs on the resulting thin tungsten oxide overlayer from Co2(CO)8 in the presence of NH3. In other words, this thin oxide overlayer affords the same selective inhibition behavior as seen on bulk WO3. In this way, both metal-on-metal and metal-on-oxide selectivity can be achieved. Cobalt films grown in the absence and presence of ammonia have resistivities of 11–20 and 15–25 μΩ cm, respectively.

Evolution of Condensable Fine Particle Size Distribution in Simulated Flue Gas by External Regulation for Growth Enhancement.

Condensation fine particles (CFPs) from coal-fired flue gas harm humans and the environment after being emitted into the atmosphere. Given their small size (<0.1 μm), difficulty arises in efficiently removing CFPs by wet electrostatic precipitators and mist eliminators. In this work, a laboratory apparatus was used to study the CFP growth under simulated power plant conditions. Four methods were independently investigated to increase the particle size: addition of ammonia, addition of fly ash, decreasing temperature, and applying an electrical discharge. Results demonstrated that the CFP size distribution possessed a unimodal structure with peak at 0.05 μm. At increased ammonia concentration from 10 to 30 ppm, the peak of growth factor shifted rightward and increased from 1.21 to 1.35 and the range of growth factor >1 was significantly broadened due to joint action of multiple mechanisms. Fly ash acted as the core, and CFPs adhered to the ash surface when forming ash-salt droplets. Cooling flue gas could also enhance the CFP growth due to vapor condensation. At decreased temperature from 45 to 30 °C, the median diameter of CFPs increased by 15%. Finally, the growth and agglomeration of CFPs can be further enhanced when an external electrical field was utilized. The size range of growth factor >1 can be broadened, and the peak growth factor significantly increased at 8 kV applied voltage. The research findings provide valuable guidance for effectively improving the CFP removal efficiency by external regulation for growth enhancement.

Nitrogen Source Affects the Composition of Metabolites in Pepper (Capsicum annuum L.) and Regulates the Synthesis of Capsaicinoids through the GOGAT-GS Pathway.

Phytochemical analyses of pepper fruit metabolites have been reported; however, much less is known about the influence of different forms of nitrogen (N), which is critical for plant growth and fruit quality formation. The “Longjiao No. 5” variety (Capsicum annuum L.) grown in Northwestern China was profiled using liquid chromatography–mass spectrometry (LC–MS) coupled with multivariate data analysis to explore the composition of different metabolites in pericarp and placenta, and to investigate the effect of three ammonium (NH4+) to-nitrate (NO3−) ratios (0:100, 25:75, and 50:50). A total of 215 metabolites were obtained by qualitative analysis, where 31 metabolites were the major differential metabolite components of pepper fruits between placenta and pericarp, and 25 among N treatments. The addition of ammonium up-regulated carbohydrates, such as α-lactose and sucrose, as well as phenylalanine lyase (PAL) of placenta tissue. The supply of 25% NH4+–N and 75% NO3−–N exhibited a relatively higher levels of ascorbic acid in pericarp and amino acids, capsaicin, and dihydrocapsaicin in placenta, and led to higher fruit weight among the ammonium-to-nitrate ratios. The expression and activities of glutamic acid synthetase (GOGAT) and glutamine synthetase (GS) that are involved in ammonium assimilation were affected by adjusting the ammonium–N proportion, and they were significantly positively correlated with capsaicin, dihydrocapsaicin contents, capsaicinoid synthetase (CS), as well as the relative expression levels of genes related to capsaicinoid biosynthesis, such as acyltransferase 3 (AT3) and acyl-ACP thioesterase (FatA).

Effects of concentration and pressure on the aqueous solvation structure of ammonia and composition dependent ion solvation scenario in water-ammonia mixtures

The hydrogen bonding structure of water and its dynamics in aqueous ammonia solution is investigated by using classical molecular dynamics simulations. We have considered eight different mole-fraction of ammonia, ranging from xNH3 = 0.02 to 0.30, and the pressure variation is carried out on the concentrated ammonia solution (xNH3=0.30), ranging from P = 0.1 MPa to 800 MPa, at 293K. The radial distribution function indicates that the addition of ammonia facilitates the structural organization of water, which is further supported by increasing values of asphericity parameter. But, the tetrahedral order parameter values suggest an angularly disordered arrangement of water molecules. The self-diffusion coefficient values of water pass through shallow minima, whereas it increases for ammonia with ammonia concentration in the solution. The application of pressure causes a sharp decline in translation mobility of ammonia compared to water, but at very high pressure (above 600 MPa), both the species diffuse at the same rate. The rotational relaxation of ammonia is approximately three times faster than water in the solution, which further increases along with concentration as well as pressure. A similar trend is also observed in the case of structural reorganization of water-water and water-ammonia hydrogen bonds. The water-water and water-ammonia hydrogen-bond lifetimes are increasing with ammonia concentration, whereas it passes through shallow maxima with the application of pressure. In this study, we have compared two different Lennard-Jones (LJ) combination rule, which causes negligible differences in the calculated properties. The solvation scenario of different ionic (Na+, Cl−) and neutral (Cl0) solutes are also analyzed along with the coordination number. It is observed that the hydration shell of ion is mainly dominated by water molecules in the solution.

Stability limits and exhaust NO performances of ammonia-methane-air swirl flames

Ammonia is a promising fuel for heat and power generation because it is carbon-free and it can be produced from abundant chemicals and renewable energy sources. However, ammonia-air mixtures feature a low reactivity and stabilizing turbulent ammonia-air flames is challenging. In this study, the stability limits of technically-premixed ammonia-methane-air mixtures are measured for a wide range of ammonia additions in a laboratory-scale swirl burner. Results are compared to that obtained for baseline methane-air mixtures. Data show that increasing the ammonia addition increases the equivalence ratio at the lean blowout limit but also reduces the flames’ propensity to flashback. If the volume fraction of ammonia in the fuel blend exceeds a critical value, experiments also show that increasing the equivalence ratio at a fixed bulk velocity does not yield flashback and rich blow-out occurs instead. This significantly widens the range of equivalence ratios yielding stable flames. The critical ammonia volume fraction is a function of the Reynolds number and is xNH3 = 0.42 for Re = 7000 and xNH3 = 0.70 for Re = 3000. Because the ability to stabilize ammonia-methane-air flames is not practically relevant if NOx emissions are too large compared to that of conventional methane-air flames, exhaust NO concentrations are also measured. Consistent with previous studies, data show that, for non-marginal ammonia fuel fractions, good NO performances are not found for lean ammonia-methane-air mixtures and can only be achieved with slightly rich mixtures, which are within measured stability limits.

The Co-occurrence of DNRA and Anammox during the anaerobic degradation of benzene under denitrification

It was revealed that Anammox process promotes the anaerobic degradation of benzene under denitrification. This study investigates the effect of dissimilatory nitrate reduction to ammonium (DNRA) and exogenous ammonium on anaerobic ammonium oxidation bacteria (AnAOB) during the anaerobic degradation of benzene under denitrification. The results indicate that anammox occurs synergistically with organisms using the DNRA pathway, such as Draconibacterium and Ignavibacterium. Phylogenetic analysis showed 64% (16/25) and 36% (5/25) hzsB gene sequences, a specific biomarker of AnAOB, belonged to Candidatus ‘Brocadia fuldiga’ and Candidatus ‘Kuenenia’, respectively. Exogenous ammonium addition enhanced the anammox process and accelerated benzene degradation at a 1.89-fold higher average rate compared to that in the absence of exogenous ammonium and AnAOB belonged to Ca. ‘Kuenenia’ (84%) and Ca. ‘Brocadia fuldiga’ (16%). These results indicate that Ca. ‘Brocadia fuldiga’ could also play a role in DNRA. However, the diversity of abcA and bamA, the key anaerobic benzene metabolism biomarkers, remained unchanged. These findings suggest that anammox occurrence may be coupled with DNRA or exogenous ammonium and that anammox promotes anaerobic benzene degradation under denitrifying conditions. The results of this study contribute to understanding the co-occurrence of DNRA and Anammox and help explore their involvement in degradation of benzene, which will be crucial for directing remediation strategies of benzene-contaminated anoxic environment.

Water and nutrient retention in coarse-textured soil profiles from the Athabasca oil sand region

Post-mining land reclamation of Athabasca Oil Sands (AB, Canada) involves the reconstruction of soil profiles able to support a mosaic of boreal forest communities. However, the use of coarse-textured reclamation materials to recreate forest ecosystems represents a challenge in terms of soil water and nutrient availability. This work aimed to quantify nutrient leaching in reclaimed coarse-textured soils constructed with two coversoils (peat mineral mix and forest floor mineral mix) underlain by mineral materials, including a blended B/C subsoil reclamation material, lean oil sand overburden substrate, and tailing sand. Water retention and conductivity curves were estimated for each material, and their retention capacity for inorganic N and P was measured in sorption isotherm experiments. The redistribution of water, inorganic N and P five days after an intense rain event was evaluated in six different reclaimed soil profiles using a laboratory-controlled leaching experiment in 1.2-m deep columns. The redistribution of fertilizer nutrients was also measured following the addition of 15N-labelled ammonium and phosphate over the top 10 cm of the columns. In addition, a 25-day incubation experiment with the two coversoils enabled us to estimate the timing of N immobilization and nitrification processes. Our results show that, depending on the combination of materials used for land reclamation, the soil profiles may provide equal or higher amounts of inorganic N and P in the rooting zone compared to natural, coarse-textured soils of the region. Following the simulated intense rainfall, the peat-mineral mix was able to retain 44% of its initial inorganic N within the top 20 cm of the reclaimed soil profiles, while 84% of the inorganic N present in the forest floor mineral mix was leached down. Compared to the movement of water, the leaching of N down the soil profiles was slower and partly restricted by the presence of lean oil sand, and to a lesser degree tailing sand. Most of the introduced fertilizer-N remained in the first 20 cm of the soil profiles under the form of nitrate, although the incubation experiment suggested that nitrification only occurred after the simulated rainfall event. Based on our experimental data and on additional simulations of water and nutrient transport, we conclude that nutrient leaching in reclaimed soils can be significant if specific materials such as forest floor mineral material and coarse-textured subsoil are combined and when an intense rainfall occurs at a period coinciding with a high concentration of nitrate-N in the topsoil.

Enhanced Chemical Oxygen Demand Removal in the Pre-Treatment of Sludge Wastewater by Coagulation

At present, a cost-effective selection of parameters for Chemical Oxygen Demand (COD) and turbidity reduction is of great importance for wastewater treatment. Like most water treatment processes, the coagulation treatment process may sound simple but is considered as an important method for wastewater treatment as it helps to remove COD and other pollutants found in wastewater. Poly aluminum chloride (PAC) with Poly ammonia (PA) coagulants was used to study the performance of the coagulation process of sludge wastewater obtained after the dewatering process. A scanning Electron Microscope (SEM) machine was also used to compare the characteristic of the flocs produced after treatment. The influence of coagulant dosing and settling time characteristics of the flocs were examined. Based on the result, with the use of poly aluminum chloride, it shows a removal efficiency of 77.9% COD. Furthermore, with the addition of Poly ammonia (PA), a greater efficiency removal of 80.6% of COD was obtained with higher turbidity removal and better flocs cohesion. Results also indicate that varying other treatment parameters like pH and temperature for effective pre-treatment have little or no significant effect on COD as well as turbidity removal.

Preparation of FePO4•2H2O from LiFePo4 mixed with LiNixCoyMn1-x-yO2 waste material

A method for preparing battery grade FePO4?2H2O from LiFePO4 and LiNixCoyMn1-x-yO2 mixed waste is proposed. The optimum leaching conditions included: temperature of 50?C, 3:1 liquid?solid mass ratio, 3.6 HCl/FePO4?2H2O mole ratio, 0.75 H2O2/FePO42H2O mole ratio, and 2 h reaction time. The solution obtained from the leaching waste material was diluted to a 1.0 M Fe concentration, then transferred to an 1 L beaker, where temperature, pH, complexing agent, ammonia addition rate and feeding mode were studied in order to determine their effects on the precipitation, particle size and morphology of FePO4?2H2O. High precipitation rate of Fe with low percentages of Al, Ni, Co, Mn in the FePO4?2H2O is achievable when precipitation is performed at a temperature of 85?C, pH of 2.0, and 20 g L-1 complexing agent. Furthermore, it was observed that a slow addition of ammonia and a flow feeding method contributed to the production of FePO4?2H2O, with small particle sizes and a flake morphology.

Rare earths recovery by fractional precipitation from a sulfuric leach liquor obtained after phosphogypsum processing

The present work describes a process to recover rare earth elements (REEs) by selective precipitation with ammonia from phosphogypsum (PG) waste, a by-product of the phosphate industry.A pretreatment step was carried out with a solution of sodium chloride and sodium carbonate (60 g/L) in order to assure, respectively, a better solubilization of impurities and a conversion of PG to a calcite matrix easily attacked in an acid medium. Enriching a sulfuric acid solution (15%) with REEs was performed by double contacting the same acid solution with appropriate amounts of the pretreated PG by maintaining the operating conditions (L/S = 3, 100 °C and 2 h) each time. The leaching method produced a sulfuric leach liquor rich with rare earths with a final concentration of 4308 mg/L as well as two anhydrite solids. The latter, having the same level of purity, could be used safely in many industrial applications.Afterward, the progressive addition of ammonia (10%) to the REEs-rich liquor led to form three precipitates at different pH values: 1.1; 2.3 and 6. The ICP/MS analysis of the precipitation liquors showed that the optimum pH for the precipitation of REEs is 1.1 allowing their recovery with an efficiency of 98.5%; while precipitations at higher pH of 2.3 and 6 had a lower recovery yield of respectively 42.4% and 39.3%. The X-ray diffraction analysis of the precipitate obtained at pH 1.1 showed that it corresponds to an ammonium sulfate compound. Analyzes with photoluminescence technique showed the characteristic luminescence bands of Ce3+, Gd3+, Dy3+, Pr3+ and Sm3+(after excitations at λExc = 260 nm and λExc = 440 nm) confirming the presence of REEs in the precipitate.

Vegetative and Physiological Responses of “Emerald” Blueberry to Ammoniacal Sources with a Nitrification Inhibitor

The nitrogen nutrition in blueberry has been studied by some authors; however, the effect of N-nitrate or N-ammoniacal fertilizers with nitrification inhibitors on plant growth and physiology has not been known. The aim of this investigation was to study the effectiveness and physiological implications of ammoniacal fertilizers, with or without nitrification inhibitors in blueberry. An experiment was conducted on 1-year “Emerald” blueberries grown in 20-L plastic pots. Our data indicate that ammonium-containing fertilizers promote vegetative growth and increase the leaf nitrogen concentration and gas exchange in plants, possibly due to higher nitrogen root absorption compared with nitrate. On the other hand, fertilization with ammonium with a nitrification inhibitor increases the leaf chlorophyll concentration compared with the addition of ammonium without a nitrification inhibitor and nitrate. However, the ammonium supply decreases the concentration of calcium and potassium in leaves. Our data suggest, for the first time, that fertilization with ammonium accompanied by a nitrification inhibitor is an effective strategy to improve the nitrogen status and promote plant development in “Emerald” blueberry.

The Effect of Alkali Addition and Coating Time on Hydrophilic Properties of Antimocrobial Ceramic Tiles

Antimicrobial glaze is used for sanitation needs in special environments such as hospitals or schools. Antimicrobial properties of TiO 2 involve photocatalytic activity on inorganic material. A hydrophilic surface, with contact angle value <65 o , is resulted by those activity. In this study, polished tile coating was done using TiO 2 material which had been prepared through a dissolving process in sulfuric acid followed by gel formation with addition of 2 types of alkali, ammonia and ammonium bicarbonate. The TiO 2 gel formed was dispersed in aquadest and then coated on the surface of the tile by dip coating with various deposition time (3 hours, 6 hours and 53 hours). ANOVA test results represent that both main effect of alkali type and coating time, and interaction effect of these variable produce significant effects on contact angles. Addition of ammonium bicarbonate produce better hydrophilic surface on the tile than addition of ammonia. The longer coating time will increase hydrophilic characteristic of the surface.

The production of l- and d-phenylalanines using engineered phenylalanine ammonia lyases from Petroselinum crispum

The biocatalytic synthesis of l- and d-phenylalanine analogues of high synthetic value have been developed using as biocatalysts mutant variants of phenylalanine ammonia lyase from Petroselinum crispum (PcPAL), specifically tailored towards mono-substituted phenylalanine and cinnamic acid substrates. The catalytic performance of the engineered PcPAL variants was optimized within the ammonia elimination and ammonia addition reactions, focusing on the effect of substrate concentration, biocatalyst:substrate ratio, reaction buffer and reaction time, on the conversion and enantiomeric excess values. The optimal conditions provided an efficient preparative scale biocatalytic procedure of valuable phenylalanines, such as (S)-m-methoxyphenylalanine (Y = 40%, ee > 99%), (S)-p-bromophenylalanine (Y = 82%, ee > 99%), (S)-m-(trifluoromethyl)phenylalanine (Y = 26%, ee > 99%), (R)-p-methylphenylalanine, (Y = 49%, ee = 95%) and (R)-m-(trifluoromethyl)phenylalanine (Y = 34%, ee = 93%).

Nitrogen fertilization modifies organic transformations and coatings on soil biogeochemical interfaces through microbial polysaccharides synthesis

The soil-water interfaces (SWI) in soil pores are hotspots for organic matter (OM) transformation. However, due to the heterogeneous and opaque nature of soil microenvironment, direct and continuous tracing of interfacial reactions, such as OM transformations and formation of organo-mineral associations, are rare. To investigate these processes, a new soil microarray technology (SoilChips) was developed and used. Homogeneous 800-μm-diameter SoilChips were constructed by depositing a dispersed Oxisol A horizon suspension on a patterned glass. Dissolved organic matter from the original soil was added on the SoilChips to mimic SWI processes. The effects of ammonium fertilization (90 mg N kg−1 soil) on chemical composition of SWIs were evaluated via X-ray photoelectron spectroscopy. Over 21 days, ammonium addition increased OM coatings at SWIs and modified the OM chemical structure with more alcoholic- and carboxylic-C compared to the unfertilized control. Molecular modeling of OM composition at SWIs showed that N fertilization mainly facilitated the microbial production of glucans. We demonstrated that N availability modifies the specific OM molecular processing and its immobilization on SWIs, thereby providing a direct insight into biogeochemical transformation of OM at micro-scale.

Biochemical treatment of leachates from hydrometallurgical recycling of spent alkaline batteries

Recycling of waste electrical and electronic equipment including spent batteries focuses on maximizing the material recovery efficiency (of metals, polymers, or solvents) and decreasing the negative environmental impact of leachates that remain after the treatment (i.e. the secondary wastes).The major aim of this study was to develop a novel, low-cost biochemical treatment technology for the management of effluents generated during sulfuric acid–based hydrometallurgical recycling of spent alkaline batteries. We explored the use of various chemical reagents (40% NaOH, 20% Na2CO3, and 1% NH3(aq)) and biogenic ammonia produced by urea-degrading bacteria to increase the pH of the effluents (from pH 0.5 to pH 5.0) and prepare them for further treatment by sulfate-reducing bacteria. Comparisons of the pretreatment efficiency and metal and sulfate removal yields, as well as the characterization of the neutralization products (sediments and effluents) showed that the most promising results were obtained when the raw leachates were treated with 40% NaOH (to reach pH 3.5), followed by the addition of biogenic ammonia (to reach pH 5.0). Sulfate-reducing bacteria (SRB) activity led to a further pH increase (up to ~7.3), almost complete (99%) sulfate removal and metal sulfide (ZnS, MnS) precipitation, as up to ~99% of Zn and Mn were removed in SRB cultures to which appropriately diluted pretreated leachates had been added. The presented study indicated that the pretreatment and neutralization of hydrometallurgical effluents based on the use of urea-degrading and sulfate-reducing bacteria could be an attractive alternative to conventional chemical treatment.